Chapter 17: Phenomena Phenomena: Mass Moles Boiling Freezing - - PowerPoint PPT Presentation

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Chapter 17: Phenomena

Phenomena: Different masses

• f solute were

added to 1 kg of either H2O or

• C6H6. The boiling

and freezing points of the solutions were then measured. Examine the data to determine patterns in how these variables affect the boiling and freezing points of the solutions.

H2O Exp. Solute Mass

• f Solute

Moles

• f Solute

Boiling Point Freezing Point 1 None 0.0 g 0.00 mol 100.0˚C 0.0˚C 2 NaCl 50.0 g 0.85 mol 100.9˚C

• 3.2˚C

3 NaCl 100.0 g 1.71 mol 101.7˚C

• 6.4˚C

4 K2O 50.0 g 0.53 mol 100.8˚C

• 3.0˚C

5 K2O 107.0 g 1.14 mol 101.7˚C

• 6.3˚C

6 C12H22O11 1169.0 g 3.42 mol 101.7˚C

• 6.4˚C

7 NaHCO3 71.7 g 0.85 mol 100.9˚C

• 3.2˚C

8 C6H12O6 616.1 g 3.42 mol 101.7˚C

• 6.4˚C

C6H6 Exp. Solute Mass

• f Solute

Moles

• f Solute

Boiling Point Freezing Point 1 None 0.0 g 0.00 mol 80.1˚C 5.5˚C 2 NaCl 50.0 g 0.85 mol 84.4˚C

• 3.2˚C

3 NaCl 100.0 g 1.71 mol 88.7˚C

• 12.0˚C

4 K2O 50.0 g 0.53 mol 84.1˚C

• 2.7˚C

5 K2O 107.0 g 1.14 mol 88.7˚C

• 11.9˚C

6 C12H22O11 1169.0 g 3.42 mol 88.7˚C

• 12.0˚C

7 NaHCO3 71.7 g 0.85 mol 84.4˚C

• 3.2˚C

8 C6H12O6 616.1 g 3.42 mol 88.8˚C

• 12.0˚C

Chapter 17 Properties of Solutions

• Types of Solutions
• Solubility
• Colligative Properties
• Vapor Pressure
• Boiling and Freezing Point
• Osmotic Pressure

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Big Idea: Liquids will mix together if both liquids are polar or both are

• nonpolar. The

presence of a solute changes the physical properties of the

• system. For non-

volatile solutes the vapor pressure, boiling point, freezing point, and osmotic pressure are only dependent

• n the number of

ions/particles.

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Types of Solutions

Matter can be broken in to two subcategories: pure substances and mixtures. Pure Substances

 Elements: A substance that cannot be

separated into simpler components by chemical techniques.

 Compounds: A specific combination of elements

that can be separated into its elements by chemical techniques but not by physical techniques.

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Examples Examples: : Water (H2O), salt (NaCl), and sucrose (C12H22O11)

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Types of Solutions

Mixtures

 Heterogeneous Mixtures: A mixture in which the

individual components, although mixed together, lie in distinct regions that can be distinguished with an optical microscope.

 Homogeneous Mixture: A mixture in which the

individual components are uniformly mixed, even on the molecular scale.

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Example: Example: Air (nitrogen, oxygen, argon, …)

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Types of Solutions

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Student Question

Types of Solutions

How many of the following are homogeneous mixtures? Oil and vinegar Salt water Chalk and table salt Kool-Aid Charcoal and sugar

a) 1 is homogeneous b) 2 are homogeneous c) 3 are homogeneous d) 4 are homogeneous e) All are homogeneous

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Types of Solutions

 Solution: A homogeneous mixture.

Solutions are made up of at least two parts

 Solvent: The most abundant component of a solution.  Solute: A dissolved substance.

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State of Solution State of Solvent State of Solute Example Gas Gas Gas Air Natural gas Liquid Liquid Liquid Tequila Antifreeze Liquid Liquid Gas Soda water Liquid Liquid Solid Sea water Sugar water Solid Solid Solid Alloys (Steel or brass) Solid Solid Gas Hydrogen in platinum

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Student Question

Types of Solutions

The density of a 40.0% by weight aqueous solution of NaOH is 1.432 𝑕

𝑑𝑛3. What is the

molality of NaOH? Helpful Information: 𝑁𝑂𝑏𝑃𝐼 = 40.00 𝑕

𝑛𝑝𝑚

a) 12.9 m b) 14.3 m c) 16.7 m d) 13.8 m e) None of the above

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Solubility

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Exothermic Endothermic

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Student Question

Solubility

Which one of the following substances would be the most soluble in CCl4?

a) CH3CH2OH b) C10H22 c) H2O d) NaCl e) NH3

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Solubility

Cation and H2O Anion and H2O

 Hydration: The reaction of a substance with

water.

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Not

• te:

e: For molecules, the extent of hydration increases as polarity increases. Not

• te:

e: For ions, the extent of hydration increases as charge density (charge per volume) increases. In general, the smaller the size, the larger the charge density and the larger the charge, the larger the charge density.

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Solubility

 Saturated Solution: A solution that holds the

maximum amount of solute.

 Unsaturated Solution: A solution that holds less

than the maximum amount of solute.

 Supersaturated Solution: A solution that holds more

than the maximum amount of solute.

If a solutions is

supersaturated any small disturbance can cause the solute to recrystallize

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Solubility

 The graph shows the

saturation level of different solutions at a given temperature. If a solution has a solubility that results in a point above the line, then the solution is considered to be supersaturated. However, if a solution has a solubility that results in a point under the line, then the solution is considered unsaturated.

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Solubility

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H gas

P k  

Not

• te:

e: Where 𝝍 is the mole fraction of the gas dissolved in solution. Not

• te:

e: An alternate form of henry’s Law is: P = 𝑙𝐼𝑑 where c is the molarity.

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Colligative Properties

 Colligative Properties: Physical properties of

solutions that depend on the number of solute particles present but not the type of solute particles.

 Examples of Colligative Properties:

 Vapor Pressure (non volatile solutes)  Freezing Point  Boiling Point  Osmotic Pressure

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Vapor Pressure

 Vapor Pressure: The pressure exerted by the vapor of

a liquid or solid.

 Volatile: Having a high vapor pressure at ordinary

temperatures (evaporates easily).

 Nonvolatile: Having a low vapor pressure at ordinary

temperatures (does not evaporate easily).

Nonvolatile Solute

 Raoult’s Law

𝑄𝑡𝑝𝑚𝑣𝑢𝑗𝑝𝑜 =

𝜓𝑡𝑝𝑚𝑤𝑓𝑜𝑢𝑄𝑡𝑝𝑚𝑤𝑓𝑜𝑢

°

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Not

• te:

e: Where 𝝍 is the mole fraction of the solvent

𝑜𝑡𝑝𝑚𝑤𝑓𝑜𝑢 𝑜𝑢𝑝𝑢

.

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Student Question

Vapor Pressure

Which of the following aqueous solutions containing nonvolatile solutes should have the highest boiling point?

a) 0.02 m C6H12O6 b) 0.02 m (NH4)2SO4 c) 0.02 m NaCl d) 0.02 m Ce(NO3)4 e) All have the same boiling point

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Vapor Pressure

Ideal Solution (Obeys Raoult’s Law)

Which substance (A

• r B) has the higher

boiling point?

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Student Question

Vapor Pressure

What is the vapor pressure of a solution of 50.0 g of CCl4 and 50.0 g of CHCl3 at 25˚C. The vapor pressures at 25˚C for pure CCl4 and CHCl3 are 98.3 torr and 172.0 torr respectively. Helpful Information: 𝑁𝐷𝐼𝐷𝑚3 = 119.37 𝑕

𝑛𝑝𝑚 and

𝑁𝐷𝐷𝑚4 = 153.81 𝑕

𝑛𝑝𝑚

a) 131 torr b) 140. torr c) 149 torr d) 126 torr e) None of the Above

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Vapor Pressure

Deviations from Raoult’s Law

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Ideal ΔH=0

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Boiling and Freezing Points

 Freezing Point Depression: The decrease in the

freezing point of a solvent caused by the presence of a solute.

 Boiling Point Elevation: The increase in the boiling

point of a solution caused by the presence of a solute.

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Boiling and Freezing Points

Boiling Point Elevation

 The presence of a nonvolatile solute lowers the vapor

pressure of the solution, therefore, a higher temperature must be present in order for the vapor pressure of the solution to reach 1 atm (normal boiling point).

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solid liquid gas

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Boiling and Freezing Points

 At the freezing point, the solid and the liquid are

in equilibrium. Both Beakers are at 0°C

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Pure H2O Ice and Water at Equilibrium H2O and Nonvolatile Solute Ice and Water not at Equilibrium

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Boiling and Freezing Points

Freezing Point Depression

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solid liquid gas

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Boiling and Freezing Points

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Boiling and Freezing Point Data Solvent Boiling Point Kb Freezing Point Kf H2O 100.0 0.51 0.0 1.86 CCl4 76.5 5.03

• 22.99

30. CHCl3 61.2 3.63

• 63.5

4.70 C6H5 80.1 2.53 5.5 5.12 CS2 46.2 2.34

• 111.5

3.83 C4H10O 34.5 2.02

• 116.2

1.79 C10H16O 208.0 2.95 179.8 40.

 

C 

 

mol kg C 

 

C 

 

mol kg C 

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Student Question

Boiling and Freezing Points

A solution of 0.640 g of azulene in 100.0 g of benzene boils at 80.230˚C. The boiling point of benzene is 80.100˚C; the Kb is 2.53 ℃∙𝑙𝑕

𝑛𝑝𝑚 . What is

the molecular weight of azulene? Helpful Information: The van’t Hoff factor is 1 for azulene.

a) 108 𝑕

𝑛𝑝𝑚

b) 117 𝑕

𝑛𝑝𝑚

c) 134 𝑕

𝑛𝑝𝑚

d) 99 𝑕

𝑛𝑝𝑚

e) None of the Above

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Osmotic Pressure

 Osmosis: The flow of solvent from a lower

concentration solution through a semipermeable membrane to a higher concentration solution

 Osmotic Pressure: The pressure needed to stop

the flow of solvent through a semipermeable membrane.

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Osmotic Pressure

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Take Away From Chapter 17

 Big Idea: Liquid will mix together if both liquids are

polar or both are nonpolar. The presence of a solute changes the physical properties of the system. For non-volatile solutes the vapor pressure, boiling point, freezing points, and osmotic pressure are only dependent on the number of ions/particles.

 Types of Solutions

 Know the difference between homogeneous and

heterogeneous mixtures

 Homogeneous Mixtures: Uniformly mixed (air)  Heterogeneous Mixtures: Not uniformly mixed (chocolate

chip cookie)

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Numbers correspond to end of chapter questions.

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Take Away From Chapter 17

 Types of Solutions (Continue)

 Know the definition of a solution  Solution: Homogeneous mixture  Be able to determine solution composition (15,16,17)

 Molarity  𝑁 =

𝑜𝑡𝑝𝑚𝑣𝑢𝑓 𝑊𝑡𝑝𝑚𝑣𝑢𝑗𝑝𝑜

 Mole Fraction  𝜓𝐵 =

𝑜𝐵 𝑜𝑢𝑝𝑢𝑏𝑚

 Mass Percent  𝑛𝑏𝑡𝑡 % 𝐵 =

𝑛𝐵 𝑛𝑢𝑝𝑢𝑏𝑚 100%

 Molality  𝑛 =

𝑜𝑡𝑝𝑚𝑣𝑢𝑓 𝑛𝑡𝑝𝑚𝑤𝑓𝑜𝑢

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Numbers correspond to end of chapter questions.

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Take Away From Chapter 17

 Solubility

 Be able to predict whether two substance are soluble (33,34)

 Like dissolves like  Two polar substances are soluble with each other  Two nonpolar substances are soluble with each other  A nonpolar and a polar substance are not soluble with each

• ther

 Be able to predict the extent of hydration (32)

 The more polar the ion/molecule the greater the hydration  The greater the charge density the greater the hydration (In

general the smaller the ion/molecule the greater the hydration and the larger the charge the greater the hydration)

 Know the effects of temperature on solubility

 In general the greater the temperature the higher the solubility of

a solid in a liquid

 The greater the temperature the lower the solubility of a gas in a

liquid

 Know the effects of pressure on the solubility of a gas (39)

 𝑄 = 𝑙𝐼𝜓

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Numbers correspond to end of chapter questions.

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Take Away From Chapter 17

 Colligative Properties  Vapor Pressure

 Be able to calculate the vapor pressure of a solvent and

a nonvolatile solute (42,44,47,79)

 𝑄𝑡𝑝𝑚𝑣𝑢𝑗𝑝𝑜 = 𝜓𝑡𝑝𝑚𝑤𝑓𝑜𝑢𝑄𝑡𝑝𝑚𝑤𝑓𝑜𝑢

°

 Be able to calculate the vapor pressure of solvent and

volatile solute (49,51)

 𝑄𝑡𝑝𝑚𝑣𝑢𝑗𝑝𝑜 = 𝜓𝑡𝑝𝑚𝑤𝑓𝑜𝑢𝑄𝑡𝑝𝑚𝑤𝑓𝑜𝑢

°

+ 𝜓𝑡𝑝𝑚𝑣𝑢𝑓 𝐵𝑄𝑡𝑝𝑚𝑣𝑢𝑓 𝐵

°

+ ⋯

 Be able to construct mole fraction vs. vapor pressure

plots (52,53,54,55,57)

 Know what a positive deviation to Raoult’s Law implies  ΔH>0: solute/solvent interaction are weaker than

solute/solute interactions or solvent/solvent interactions

 Know what a negative deviation of Raoult’s Law implies  ΔH<0: solute/solvent interaction are stronger than

solute/solute interactions or solvent/solvent interactions

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Numbers correspond to end of chapter questions.

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Take Away From Chapter 17

 Boiling and Freezing Points

 Be able to determine the van’t Hoff factor (i) and know

how this factor effects colligative properties (13,81,82)

 Be able to calculate freezing point and boiling point of a

solution (62,63,70,74,124)

 𝑈

𝑔 = 𝑈 𝑔 ° − ∆𝑈 𝑔 or 𝑈𝑐 = 𝑈𝑐 ° + ∆𝑈𝑐

 ∆𝑈

𝑔 = 𝑗𝐿 𝑔𝑛 or ∆𝑈𝑐 = 𝑗𝐿𝑐𝑛

 Osmotic Pressure

 Be able to calculate osmotic pressure (71,117)

 𝛲 = 𝑗𝑁𝑆𝑈

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Numbers correspond to end of chapter questions.